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What is the Solar system?

The solar system is the Central star, the Sun and all the cosmic bodies that revolve around it.

The structure of the Solar system

In the solar system 8 the largest celestial bodies or planets. Our Earth is also a planet. In addition to her around the Sun make its journey in space 7 planets: mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune. The last two from the Ground can only be observed through a telescope. The remaining visible to the naked eye.

More recently, the number of planets reckoned another celestial body Pluto. He is very far from the Sun, beyond the orbit of Neptune, and was opened in 1930. However, in 2006, astronomers have introduced a new classic definition of a planet, and Pluto don't make it horrible.

Comparative sizes of the Sun and planets of the Solar system

The planet known to people since ancient times. The nearest neighbors of the Earth - Venus and Mars, the most distant from it - Uranus and Neptune.

Large planets can be divided into two groups. The first group includes the planets that are closest to the Sun: it is the terrestrial planets, or inner planets, mercury, Venus, Earth and Mars. All these planets have a high density and a hard surface (although it is liquid core). The largest in this group of planet Earth. However, far from the Sun and the planets Jupiter, Saturn, Uranus and Neptune significantly superior to the Earth in size. Therefore they are called giant planets. They are also called the outer planets. Thus, the mass of Jupiter is greater than the mass of the Earth is more than 300 times. Giant planets are significantly different from the terrestrial planets according to their structure: they do not consist of heavy elements, and of gas, mainly hydrogen and helium, like the Sun and other stars. Planets-giants do not have a solid surface is just gas balls. So they are called gaseous planets.

Between Mars and Jupiter is the belt of asteroids, or minor planets. An asteroid is a small planetologie body of the Solar system, ranging in size from a few meters to thousands of kilometers. The largest asteroids in this belt is Ceres, Pallas and Juno.

Beyond the orbit of Neptune is another belt of small celestial bodies, which is called the Kuiper belt. It is 20 times wider than the asteroid belt. Pluto, who lost the status of a planet and was classified as dwarf planets, is precisely in this zone. In the Kuiper belt, there are other dwarf planets similar to Pluto, in 2008 was named plutoid. This makemake are carved on rocks and Haumea. By the way, Ceres from the asteroid belt also belong to the class of dwarf planets (but not plutoids!).

Another plutoid - Eris - size comparable to Pluto, but is much farther from the Sun in the Kuiper belt. Interestingly, Eris one time there was even a candidate for the 10th planet in the Solar system. But ultimately, it is the discovery of Eris (caused a review of the status of Pluto in 2006 when the international astronomical Union (IRU) has introduced a new classification of celestial bodies in the Solar system. According to this classification, Eris and Pluto are not under the notion of the classical planets, and "earned" only the title of the dwarf planets, heavenly bodies that revolve around the Sun, are not satellites of the planets and have a fairly large mass in order to maintain a nearly round shape, but, unlike the planets, is not able to clear its orbit from other space objects.

In the composition of the Solar system beyond the planets are their satellites, which revolve around them. All satellites currently account for 415. Constant companion of the Earth - Moon. Mars has 2 satellites - Phobos and Deimos. Jupiter 67 satellites, and Saturn - 62. 27 satellites has Uranium. And only Venus and mercury no satellites. But the "dwarfs" Pluto and Eris (the satellites are: Pluto is Charon, and Eris (- Dysnomia. However, astronomers have not yet come to a final conclusion whether the companion Charon Pluto or Pluto-Charon is so-called a double planet. Even some asteroids have satellites. Champion size among satellites Ganymede, a moon of Jupiter, slightly behind him Saturn's moon Titan. And Ganymede, and Titan exceed the size of mercury.

In addition to the planets and satellites of the Solar system through dozens or even hundreds of thousands of small bodies: caudate heavenly bodies - comets, a huge number of meteorites, dust particles of matter scattered atoms of different chemical elements, the flow of atomic particles and others.

All objects in the Solar system are held in it by the force of attraction of the Sun, and they all revolve around him, and in the same direction with the rotation of the Sun and almost in the same plane, called the Ecliptic. Exception - some comets and Kuiper belt. In addition, almost all objects in the Solar system rotate around its axis, and in the same direction as around the Sun (except for Venus and Uranus; the latter rotates and does "lying on its side").

Planets of the Solar system revolve around the Sun in the same plane - the plane of the Ecliptic

The Ecliptic of the Solar system
The orbit of Pluto is highly tilted relative to the Ecliptic (17°) and strongly stretched

The Sun is concentrated almost the entire mass of the Solar system - 99,8%. The four largest object - gas giants - make up 99% of the remaining mass (when the majority - about 90 percent - are in Jupiter and Saturn). As for the size of the Solar system, astronomers have not yet come to a consensus on this issue. According to current estimates, the size of the Solar system is not less than 60 billion kilometers. To at least approximately to imagine the scale of the Solar system, we will give a more clear example. Within the Solar system per unit distance take an astronomical unit (and. E.) - the average distance from the earth to the Sun. It is approximately 150 million km (light travels this distance in 8 min 19 s). The outer boundary of the Kuiper belt is located at a distance of 55 and. that is from the Sun.

Another way to imagine the real size of the Solar system is to imagine a model in which all dimensions and distances are reduced in a billion times. In this case, the Earth would be about 1.3 cm in diameter (about the size of a grape). The moon will rotate at a distance of about 30 cm from it. The sun is 1.5 meters in diameter (about the height of a person) and to be at a distance of 150 meters from the Ground (about a city block). Jupiter - 15 cm in diameter (the size of a large grapefruit) and at a distance of 5 city blocks from the Sun. Saturn (the size of an orange) at a distance of 10 blocks. Uranus and Neptune (lemons) - 20, and 30 blocks. People on this scale would be the size of an atom; and the nearest star is at a distance of 40 000 km